Control devices currently used in timepieces such as wristwatches are generally formed of winding crowns and pushbuttons consisting of a stem penetrating the watch casing. The stem of the crown and the pushbuttons must be longitudinally displaced to access the various functions of the watch. The stem of the crown must also be capable of rotating on its axis. This stem contacts the mechanical and/or electronic components which control the functioning of the instrument.
This type of watch presents a number of disadvantages. In particular, it is relatively difficult to ensure that the watch is sealed in the area of the crown.
A completely sealed wristwatch is described in U.S. Pat. No. 5,572,489. This document describes a wristwatch having a manually movable bezel with permanent magnets inside. Inside the watch case, near the permanent magnets, there are movable contact elements sensitive to magnetic fields which can be created by the permanent magnets.
When one of the permanent magnets is located near a contact, it closes, thereby establishing a connection between pathways on a printed circuit. The crown is made so it can assume positions corresponding to the different time zones.
Arranging the magnets this way ensures a reliable seal. However, it does not speed up conventional watch functions, such as setting time. Furthermore, a set stem must be provided in order to access conventional watch functions, making it difficult to seal the watch case in the area of the stem.
In certain critical applications such as divers' watches, in particular, where the timepiece must be watertight, it is especially difficult to completely seal the area around the watch stem, because the stem must remain movable.
Another problem arises when assembling the different components of the watch. In the majority of watches assembled using an automated process, the elements are arranged along a vertical axis. But the components associated with the stem are arranged along a horizontal axis, complicating assembly and consequently increasing costs.
British Patent Application No. GB-A-2 043 968 describes a clock for use with a kitchen range using signals to access certain programming functions for cooking. This clock comprises a set stem driving a permanent magnet. Two REED relays are placed on either side of the permanent magnet in the same plane. These relays are alternately closed and opened, producing an electrical signal which can be subsequently processed in a processing circuit.
In another embodiment of the same invention, the set stem rotates a toothed gear wheel. The REED relays are replaced by induction coils formed of conductive wire coiled on a permanent magnet. Rotating the toothed wheel generates signals in the induction coils. The frequency of these signals represents the rotation speed, while dephasing represents rotation direction.
Although this device generates electrical signals representing rotation speed and direction, it cannot be integrated into a wristwatch. In actuality, the pivoting element and the elements that are sensitive to the pivoting element are located in the same plane. In the embodiment described, this is made possible by adding a housing for these different elements to the stove. The housing is attached so that it is not affected by grease splatters. An arrangement such as this is obviously not suited to a wristwatch.